In some semiconductor processes, for example, rapid thermal processes (RTP) or other thermal processes, substrate alignment is necessary to facilitate uniform heating of the substrate. For example, substrate alignment includes aligning the substrate with the substrate support, for example, such that the substrate is centered within an edge ring or on a support surface. A well aligned substrate may ensure that the substrate is uniformly heated during a thermal process. For example, a misalignment, such as between the substrate and an edge ring, can result in non-uniform heating of the substrate along an edge thereof.
Typically, a substrate is placed on the substrate support by a transfer robot, or other similar mechanism. For example, the transfer robot may hand the substrate off to lift pins, which then lower the substrate onto the edge ring or support surface. Unfortunately, such placement mechanisms are inaccurate, and misalignment occurs which result in non-uniform heating during thermal processes.
Thus, there is a need in the art for improved methods and apparatus for aligning a substrate in a process chamber.